It is known from WO 98/40417 to eliminate smell from polymers by purging the steam or inert gas or air at elevated temperature. It is furthermore known from DE 19 729 302 that polypropylene granules can be separated from water and dried at 100 to 130° C. for dehydration.
The treatment of polymers pellets such as polypropylene and polyethylene with steam and inert gas or air at elevated temperature nevertheless causes several problems. First of all, emissions, taste and odour are not sufficiently improved for a number of applications particularly in the field of drinking water pipes and automobile parts. Standard purging furthermore only removes the monomer content to a low extent from the plastic material, whereby high amounts of volatile components remain in the material. This problem is particularly important when the polymer is subjected to visbreaking for modifying the melt index of the polymer. During storage of such polymers, the loss of volatile components from the surface of the pellets may even lead to explosive mixtures with air in the storage silos.